Piston ring



- 1942- c. F. ENGELHAIJQADT PISTON RING Filed Oct. 21, 1940 2 Sheets-Sheet l CARL F ENGELHARDT TORNEY g- 1942- c. F. ENGELHARDT 2,293,681.

PISTON RING Filed Oct. 21, 1940 2 Sheets-Shet 2 5 f n v? (4 Lg il a 3 48 36 CARL F. ENGELHARDT Patented Aug. 18, 1942 UNITED Search Room STATES PATENT OFFICE PISTON RING Application October 21, 1940, Serial No. 362,118

7 Claims.

The present invention relates to a self-expanding piston ring and it relates more particularly to a self-expanding piston ring which is preferably made of sheet metal, and so formed, constructed, and arranged as to present two relatively narrow parallel annular cylinder-contacting sealing surfaces composed of a multiplicity of sector-like sections disposed end to end in close proximity to each other so as to constitute more or less continuous annular cylinder-contacting surfaces with but a ver small gap between the sectors, and spring means forming an integral part of the piston ring and also preferabl formed of the same sheet metal of which the cylinder-contacting elements are formed, thereby to tend to expand the ring tangentially or circumferentially with a resultant radially outward expansion of the component cylinder-contacting elements thereof.

The present invention is a modification and improvement of the construction shown in applicants co-pending application Serial No, 321,- 200 filed February 28, 1940.

The piston ring of the present invention may be used both for oil control purposes in the bottom ring-receiving groove of a piston which has apertures through the piston wall for oil drainage and which may also be used in the upper ring-receiving grooves without any oil drain holes through the piston wall, for compression purposes.

For the purpose of illustrating the invention, there is shown in the accompanying drawings a form thereof which is at present preferred, since the same has been found in practice to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described.

In the accompanying drawings in which like reference characters indicate like parts:

Figure 1 represents a top plan view of a piston ring embodying the present invention as shown installed in a piston disposed within a cylinder, which is generall on line l-l of Figure 3 (the parts not being in true proportion, for purposes cf better illustration).

Figure 2 is a perspective view of a fragmentary portion of the piston ring of the present invention on a much enlarged scale with a portion broken away better to expose to view some of the internal details of construction.

Figure 3 represents a section on line 3--3 of Figure 2.

Figure 4 represents a sectional view of the upper portion of a piston showing the piston ring of the present invention disposed in each of the three ring-receiving grooves thereof.

Figure 5 represents a perspective view of a fragmentary portion of a sheet metal blank in its fiat condition of which the piston ring of the present invention may be formed, but before the cylinder-contacting elements 22 and 23 have been bent over and before the spring-forming elements 25 thereof have been formed or shaped into the springs 5| intervening the cylindercontacting elements 22 and 23.

Figures 6 and 7 represent a front view and a top elevational view, respectively, of a fragmentary portion of a strip of piston ring material like that shown in Figure 5, but after the cylinder-contacting elements 22 and 23 have been bent over and after the intervening springforming portions 25 have been formed into the generally U-shaped springs 5!, but before the strip has been completely formed into the arouate formation by the further collapsing of the U-shaped spring members 5|.

Figures 8 and 9 represent a front elevational view and a top plan view, respectively, similar to that shown in Figures 6 and 7, but after the strip has been form-ed into the generally arcuate form corresponding generally to the curvature of the cylinder in which the piston ring is to be used, by further collapsing the generally U-shaped spring members 5| and by bringing the juxtaposed radial edges 44 and 45 of the cylinder-contacting elements 22 and 23 into corresponding proximity to each other.

Figure 10 represents a fragmentary front elevational view of another embodiment of the present invention in which the spring-members are disposed alternately centered and off-centered, the oil-centered spring-members being successively above and below the center-line.

One form or embodiment of the present invention is illustrated in Figures 1 to 9 inclusive, the formation of which is illustrated in Figures 5 to 9 inclusive.

Thus, in this embodiment of the present in- Vention, a flat sheet-metal strip 20 of suitable thickness having an aggregate width 2|, is cut out in the general manner indicated in the Figure 5, to form juxtaposed upper and lower, generally sector-shaped, cylinder-contacting elements 22 and 23 with intervening, connecting.

spacer portions 24 and with spring-forming portions 25.

The spring-forming portions 25 are relatively thin strips of metal (as shown in Figure 5) and are placed off the center line of the total width 2| of the sheet-metal strip 20 in the manner shown; that is, alternate strips are placed on opposite sides of the center line. The cylindercontacting elements 22 and 23 are cut out slightly 35 and 36 at the junction with the intervening, connecting, spacer portions 24.

By reason of the fact that the spring-forming element 25 when finally made into the spring member 5| in the final piston ring, will occupy only a relatively small portion of the total area of the back wall, said back wall will be in most part an opening beneath said spring member 5|. This aperture is advantageous when the piston ring is used for oil control purposes in one or two of the lower ring-receiving grooves 21 of a three-groove piston such as is illustrated in Figure 4, or of a four-groove piston wherein the lowermost or the lower two ring-receiving grooves are provided with oil drain holes 28 extending through the piston wall 29 for oil drain ing purposes. The piston ring may also be used unchanged for compression purposes in the uppermost ring-receiving groove 3|] of the piston 3! or in the upper two ring-receiving grooves 30 and 32 as shown in Figure 4.

The longitudinal or circumferential width of the cylinder-contacting portions 22 and 23 is slightly smaller in the base dimension 42 than in the end dimension 43 or in the circumferential dimension 43, this difference being so calculated that when the cylinder-contacting elements 22 and 23 have been bent over and have been brought generally edge-to-edge as indicated in Figures 1, 2 and 9, the juxtaposed edges 44 and 45 will parallel each other and will be dis- Posed as radii in relation to the axis or center 46 of the piston.

The peripheral or cylinder-contacting edges or surfaces 41 and 48 of the cylinder-contacting elements 22 and 23, respectively, may also be given a slightly convex arcuate curvature between the ends 49 and 50 thereof corresponding to the curvature of the cylinder in which the piston ring is intended to be used, so that when the cylinder-contacting elements 22 and 23 are placed side by side in close proximity as indicated in Figures 1, 2 and 9, the successive, ad jacent, cylinder-contacting surfaces 41 and 48, respectively, will form corresponding true circles matching the circle of the cylinder.

The formation of the blanks shown in Figure 5 may be accomplished by punching operations on any suitable punch press, either manual or semi-automatic, or fully automatic, with suitable dies and punches either by step-by-step or progressive punching operations. However, if desired, the blanks shown in Figure 5 may also be formed by milling out the portions 33 and 34 or by cutting out the portions 33 and 34 on a shaper or on a broaching machine. If the portions 33 and 34 are to be cut out on a milling machine or on a shaper or on a broaching machine, several sets may be stacked together and may be milled, shaped or broached all together gangwise.

The piston ring is formed by bending over towards each other the juxtaposed cylinder-contacting elements 22 and 23 so that they more or less parallel each other as indicated in Figures 6, 7, 8 and 9 and also in Figure 2 and by corrugating or bending the spring-forming elements 25 in a generally radial direction to form a series of spaced corrugation-like or loop-like springs 5 I.

The formation of the piston ring from the blank shown in Figure 5 may be accomplished by successive bending operations performed in any suitable sequence where all the bending operations may be done more or less simultaneously to produce the result indicated in Figures 1, 2, 8 and 9. In Figures 6, 7, 8 and 9, however, I have illustrated what may be one desirable sequence of bending or forming operations although it is to be understood that this sequence may be changed, or the bending or forming operations may all be accomplished more or less simultaneously by suitable automatic or semi-automatic bending and forming jigs or fixtures or machines.

Thus, for instance, in Figures 6 and 7, I have illustrated what may be an initial stage in the formation of the piston ring wherein the cylinder-contacting elements 22 and 23 have been bent over to parallel each other and wherein the spring-forming portions 25 have been bent into an initial U-shape formation 52 preliminary to their formation into the more closed loop-shaped spring 5| shown in Figures 8 and 9. In this condition, the piston-ring-forming strip would be generally straight as indicated in Figure 7, with the juxtaposed edges 44 and 45 substantially separated from each other and in non-parallel relation. Thereafter, the generally U-shape formations 52 may be collapsed somewhat to form the more or less loop-like springs 5i with a relatively smaller gap 53 between their free ends 54 and 55; the gap 53 being sufficient, however, so that the ends 54 and 55 will not quite touch each other when the juxtaposed radial edges 44 and 45 of the cylinder-contacting elements 22 and 23 have actually contacted each other. By this final collapsing operation the piston ring material or strip is formed in a generally arcuate shape indicated in Figure 9 generally corresponding to the curvature of the cylinder in which the piston ring is to be used.

In the commercial manufacture of piston rings according to the present invention, the blank shown in Figure 5 as well as the corresponding piston ring strips shown in Figures 6, 7, 8 and 9 may be formed more or less continuously in relatively great lengths from which smaller pieces may then be cut off after the strip has been completely formed or shaped into the form shown in Figures 6 and 7, or even after it has been formed into the curved shape shown in Figures 8 and 9. The length of the individual pieces would correspond more or less accurately to the circumferential dimension of the piston ring desired. For the different sized piston rings the other dimension would also be varied to accord with the width of. the ring-receiving group, the depth of the ring-receiving group, and the diameter of the piston.

Thus, for instance, the individual pieces corresponding to the circumferential length of the piston ring could be cut oif while the strip is straight as in Figures 6 and '7 and then the shorter piece curved and completed to the form shown in Figures 8 and 9 and in Figures 1 and 2, or the strip can be curved while it is still part. of the whole piece of considerable length and formed into a generally spiral formation as it is being curved and thereafter in- Search soon dividual pieces cut off corresponding to the circumferential length of the desired diameter.

In making the iston ring, the spring members are collapsed until the juxtaposed edges 44 meet each other or abut each other and until the edges 45 likewise meet or abut each other, thereby producing the curved shape. However, when the compression pressure is released, the spring members 5| open up slightly or Spring back slightly so that the edges 44 and 45 separate from each other slightly as indicated in Figures 2, 8, and 9. However, the ciroumferential length of the piston ring is so adjusted that when the free ends 56 and 51 of the piston ring abut each other and the ring is compressed circumferentially or tangentially into the diameter of the cylinder 58, the radial edges 44 and 45 of the cylinder-contacting elements 22 and 23, respectively, will generally abut each other or will have but a very small clearance between them. It is estimated that the total or aggregate of all clearance between the successive pairs of edges 44 in the entire circumference or between the successive pairs of edges 45 in the entire circumference may be a few thousandths of an inch, perhaps .003" to .007", more or less (that is, an amount perhaps no greater than the clearance at the gap in an ordinary piston ring); it being understood that at the gap or break 68 there would be substantially no clearance as the edges 55 and 51 will abut each other. Thus, by reason of the fact that each of the bends or spring members 5| tends to open up slightly after the ring has been compressed into the cylinder as is indicated in Figure 1, there is a uniformly distributed, tangential or circumferential force between successive sections of the piston ring, that is, between successive or adjacent cylinder-contacting elements 22 and 23, respectively, and this force is in turn translated into an outward radial component force tending to force each of the cylinder-contacting elements radially outward and tending to press the cylinder-contacting edges 41 and 48 thereof into firm contact with the cylinder wall with a uniformly distributed and predetermined radial force. By reason of the fact that each pair of cylinder-contacting elements 22 and 23 is free to move radially inward or outward, more or less independently of other pairs of elements, the ring is capable of adjusting itself to irregularities in the cylinder wall, such as are produced by prolonged operation of the motor, As a result, the piston ring of the present invention is more efficient in preventing loss of power ordinarily resulting from irregularities in the cylinder wall and is, in addition, more efiicient in preventing leakage of oil through such irregularities up into the combustion chamber of the cylinder, thereby materially reducing oil consumption in such worn motors.

It will be noticed that the edges 44 of the cylinder-contacting elements 22 and the edges 45 of the cylinder-contacting elements 23 overlap the generally U-shaped or generally loopshaped spring member 5| to a slight extent.

The cylinder-contacting elements 22 and 23 are preferably (though not necessarily) staggered slightly or offset slightly in relation to each other as indicated particularly in Figures 5, 6, 7, 8, and 9, so that the edges 44 and the edges 45 are not directly in alignment with each other but are slightly offset in relation to each other, thereby tending to minimize even a tendency to blow-by." If desired, this staggering may be more accentuated than that shown in the drawings.

In the manufacture of the piston ring of the present invention, I may also grind-finish the cylindrical periphery 59 of the completed ring by clamping the finished ring axially between suitable supporting discs upon a suitable mandrel or any suitable fixture, while the ring is generally fully compressed, and then grinding the periphery 59 to match the cylinder, by rotating the ring about its axis against a revolv ing grinding wheel. If desired, a number of piston rings may be so clamped and held side by side on the same fixture or on the same mandrel between the same clamping discs or blades, so that they may be ground altogether to match the cylinder.

The gap or break 68 in the piston ring may be formed through the pair of juxtaposed cylinder-contacting elements 22 and 23 as indicated in Figures 1 and 2.

The piston ring of the present invention is highly effective both for oil control as well as for compression, and may be used without any separate expander spring and will produce a suitably high cylinder-contact pressure per unit of area between the cylinder-contacting surfaces of the piston ring and the cylinder wall. However, the resilient strength of the spring member 5| is adjusted to prevent too-high cylinder-contact pressure 50 that there will be no scoring of the cylinder wall and so that there will be little variation in the pressure of sizes ranging from standard diameter to slightly oversize. (.060 oversize, for example).

The piston ring of the present invention is preferably made of sheet steel of suitable consistency or suitable hardness although it may be made of other sheet metals, such as sheet bronze or sheet brass or other suitable alloy, both ferrous and non-ferrous. If the piston ring is made out of sheet steel, it may be formed out of fully annealed sheet steel but one capable of being subsequently hardened and tempered to a suitable degree of hardness and also to impart a suitable degree of resiliency to the spring members 5|. Thus, for instance, the blank shown in Figure 5 may be formed while the metal is completely annealed and the formation shown in Figures 6 and 7 and even the formation shown in Figures 8 and 9 may b made while the metal is fully annealed, although these formations may also be formed with a certain amount of hardness setting into the metal by suitable hardening and tempering. The final hardening and tempering, however, should preferably be done before the cylinder-contacting circumference of the completed ring is grindfinished or otherwise finished to the cylinder diameter.

The piston ring of the present invention is particularly efficient in preventing an excessive pressure upon and scoring of the cylinder wall and in providing a high degree of oil drainage. As described hereinbefore, that portion of the back wall directly opposite each of the springforming members 5| is completely open and the piston ring thereby permits of very efficient drainage of oil therethrough.

The spring-forming members 5| are placed off-center with relation to the back wall of the piston ring and are staggered so that alternate spring members are respectively axially above and below the center line. This structure has been found to increase the strength of the piston ring against axial displacement as compared to the strength of a ring having similar sized spring-forming elements arranged uniformly at the center line. This advantage is especially important when the spring-forming member 5| must be made in the form of an extremely thin strip (this is frequently necessary to prevent excessive radial outward pressure when the piston ring is formed of an especially thick or stiff metal).

It is possible to make one of the cylindercontacting elements 22 or 23 of a shorter length than the other so that it does not actually make contact with the cylinder, and it is further possible to omit one of said elements completely. In such a case, each piston ring would present only a single narrow annular rib making contact with the cylinder; the spring members 5| then merely acting as a supporting ring and spacing ring.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing de scription to indicate the scope of the invention.

It is possible to have said members 5| placed off-center without being alternately above and below the center line; for example, two might be successively below the center line and the next two above and so on.

It is also possible to have some of the spring members centered while others are off-center; for example, one below, one centered, one above, one centered, one below and so on. Thus, in Figure 10, there is shown another embodiment of the present invention in which the springmembers are alternately centered and off-centered; the off-centered spring-members being successively below and above the center-line. That is. in the embodiment shown in Figure 10, the order of spring-members is as follows:

Spring-member fil-a (below the center-line), spring-member 5| on the center-line), springmem-ber 5|'-b (above the center-line), springmember 5! (on the center-line), spring-member 5l-a (below the center-line) and so on.

Having thus described the invention, what is hereby claimed as new and desired to be secured by Letters Patent is:

1. A one-piece, flexible. self-expanding piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of sprin material extending in a generally radial direction, said crests being radially outermost and being formed of single relatively narrow strips substantially axially displaced from the center line of said ring thereby to provide substantial oil passages adjacent said crests, a pair of more or less parallel, integrally formed extensions projecting from each of said troughs radially outwardly beyond said crests, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs.

2. A one-piece, flexible. self-expanding, piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring material extending in a generally radial direction, said crests being radially outermost and being formed of relatively narrow strips axially displaced from the center line of said ring, successive crests being alternately above and below said center line, a pair of more or less parallel, integrally formed. extensions projecting from each of'said troughs radially outwardly beyond said crests, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs,

3. A one-piece, flexible. self-expanding, piston ring composed of alternating crests and troughs of spring material extending in a generally radial direction, said crests bein radially outermost and being formed of single relatively narrow strips substantially axially displaced from the center line of said ring thereby to provide substantial oil passages adjacent said crests, a pair of more or less parallel, integrally formed, extensions projecting from each of said troughs radially outwardly beyond said crests, to form a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs, the circumferential dimension of said ring being such that it will be compressed slightly when confined in a cylinder, whereby said corrugated annulus will tend to urge each of said extensions radially outward, the resilient strength of said corrugated annulus being sufficient to keep said extensions in firm contact with the adjacent portion of the cylinder wall.

4. A selfexpanding, flexible piston ring formed of sheet metal comprisin a series of generally adjacent sections each including a pair of generally parallel side walls and a back panel formed integrally therewith, said side walls having a larger circumferential dimension than said back panel, together forming a generally U- shaped cross-section in a plane in which the axis of the ring lies, a relatively narrow spring member connecting successive pairs of adjacent sections, said spring members being axially displaced from the center line of said pistonring, successive spring members being alternately above and below said center line, said spring members being formed integrally with and in continuation of said back panels, said pairs of side walls forming a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs, the side walls of each section being circumferentially staggered in relation to each other.

5. A one-piece, flexible. selfexpanding piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring material extending in a generally radial direction, said crests being radially outermost and being formed of single relatively narrow strips, some of said strips being substantially axially displaced from the center line of said ring, substantial oil passages being thus provided axially adjacent said strips, a pair of more or less parallel, integrally formed extensions projecting from each of said troughs radially outwardly beyond-said crests, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, axially separated, an nular, cylinder-contacting ribs.

6. A one-piece, flexible, self-expanding piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring material extending in a generally radial direction, said crests being radially outermost and being formed of single relatively narrow strips, some of said strips being substantially axially displaced from the center line of said ring, successive strips being alternately centered and substantially off-centered, substantial oil passages being thus provided axially adjacent said strips, a pair of more or less parallel, integrally formed extensions projecting from each of said troughs radially outwardly beyond said crests, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs,

7. A one-piece, flexible, self-expanding piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring material extending in a generally radial direction, said crests being radially outermost Search Room and being formed of single relatively narrow strips, some of said strips being substantially axially displaced from the center line of said ring, successive strips being arranged one below center, one on center, one above center, one on center, one below center and so on, substantial oil passages being thus provided axially adjacent said strips, a pair of more or less parallel, integrally formed extensions projecting from each of said troughs radially outwardly beyond said crests, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, axially separated, annular, cylinder-contacting ribs.

CARL F. ENGELHARDT.

Dedication 2,293,68L-0arl F. Engelhardt, Yeadon, Pa. PISTON RING. Patent dabed Aug. 18, 1942. Dedication filed Feb. 16, 1955, by the asslgnee, Thompson Products, Inc.

w Hereby dedicates to the public the entire remaining term of said patent.

[Official Gazette M arch 15, 1.955.] 

